This invention relates generally to sensor probes and, more particularly, to a universal magnetic sensor probe for use in the slot of an electrical machine wherein the probe includes adjustable members for use in a variety of electrical machines with different slot openings.
In the field of generating and utilizing electricity, it is important that elements of an electrical machine system remain fully functional over their expected working life so that unexpected downtimes and/or catastrophic failures can be avoided. To avoid such problems, it is important that elements such as large stators, which form part of the electrical machine systems are carefully inspected and tested during regular periodic maintenance or before being sold and installed, in particular, prior to electric power generating installation.
The stator core of electric machines utilizes thin insulated steel laminations to enable flux penetration and to reduce the eddy current flow for higher efficiency operation. The laminations are often stacked by placing a dovetail groove of the laminations in a dovetail of a key bar, which is attached to the frame. To hold the laminations together and to prevent lamination vibration, the core is axially clamped with a force of about 300˜350 pound per square in (psi) (2.07 megapascal (MPa)˜2.41 MPa).
Short circuiting one lamination to another lamination can be caused by manufacturing defects, damage during assembly/inspection/rewind, stator-rotor contact, vibration of loose coil wedges/laminations, foreign magnetic material, etc. If the laminations are short circuited for any reason, a circulating fault current is induced. The circulating fault current increases with the number of shorted laminations and the conductivity between the laminations and the short/key bar. The fault current increases the power dissipation in the stator core and causes localized heating. The hot spots can progress to more severe localized heating and eventually cause burning or melting of the laminations. As a result, the stator bar insulation and windings can also be damaged causing ground current flow through the stator core and total destruction of the machines. Therefore, inter-laminar faults should be detected and repaired while damage is minor to prevent escalating damage and to improve the reliability of electric machine operation. Such faults may be detected by a sensor probe positioned within a slot opening of an electrical machine where variations in leakage flux produced with the stator suitably energized may be monitored.
Electric machines (e.g., generators, motors, etc.) of different designs will invariably have different widths of slot openings. In particular, different manufacturers provide electric machines having lamination teeth in varying sizes. Further, slot openings between the lamination teeth are also of different widths and sizes. As a result, a set of as many as 12-15 different sensor probes may be required to accommodate the varying slot openings of electric machines. There may be some instances where an exact fit or a desired air gap cannot be achieved by the pre-fabricated sensor probes. Therefore, inefficiencies such as higher manufacturing costs and increased efforts will result.
These and other drawbacks exist in current systems and techniques.